Line-above-ground to hollow waveguide coupling



J. A. KosTRlzzA ErAL Filed Jan. 9, 1953 LINE-ABOVE-GROUND TO HOLLOW WAVEGUIDE COUPLING April 1, 1958 lNvEN'roRs 8 10M 4. wsrf/2A PA uz 75m/wam BY ATTORNEY United States Patent LINE-ABOVE-GRUND TO HOLLOW WAVEGUDE CUPLING John A. Kostriza, New Dorp, and Paul Terranova, Brooklyn, N. Y., assignors to International Telephone and Telegraph Corporation, a corporation of Maryland Applicationlanuary 9, 1953, Serial No. 330,469

12 Claims. (Cl. 333-26) This invention relates to microwave transducers and more particularly to transducer arrangements for coupling microwave energy between two different types of waveguides.

In the copending applications of D. D. Grieg and H. F. Engelmann, Serial No. 227,896, led May 23, 1951, now abandoned, and Serial No. 234,502, filed June 30, 1951, now abandoned, and M. Arditi and P. Parzen, Serial No. 286,764, tiled May 8, 1952, now Patent No. 2,774,046, microwave waveguides comprising generally a lineabove-ground type of transmission line, over which microwave energy may be propagated in a mode simulating a TEM mode are shown. In this type of transmission line, a planar conductor is employed as a ground conductor with a line conductor disposed in spaced parallel relation thereto by means of a strip or layer of dielectric material. The line and planar conductors are preferably of different widths, that is, the planar conductor is made wider than the line conductor so that it appears as an infinite conducting surface to the line conductor, thereby insuring an electric iield distribution characterized generally by the TEM mode. For example, the ield distribution is believed to be similar to that which occurs between one of the conductors of a truly parallel conductor system and the neutral plane between such conductors. The important parameters of this type of transmission line are the width of the line conductor and the dielectric spacing between the line conductor and the planar conductor. v Y

One of the objects of this invention is to provide a transducer for coupling microwave energy between a lineabove-ground type of waveguide and a rectangular type of waveguide; and a further object is to make the transducer arrangement so that the coupling of energy propagated is obtained without appreciable distortion of the mode of propagation.

A feature of the invention involves the extension of a line-above-ground type of waveguide into the rectangular type of waveguide and to provide the portion of the lineabove-ground waveguide with suitable conductive structure to effect proper excitation of the electric and magnetic elds within the rectangular waveguide for propagation of energy in the TEM, mode. Several diierent arrangements of the transducer portion of the line-aboveground waveguide are possible, one being the provision of an enlarged area of the conducting line within the rectangular waveguide and still another is the provision of the conductive post disposed substantially axially of the rectangular waveguide in coupled relation to the line conductor. Still other arrangements include the provision of conductors disposed at right angles to the line conductor extending partially or entirely across the rectangular waveguide, as the case may be.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

2,829,348 Patented Apr. l, 1958 Figure 1 is a longitudinal cross-sectional view showing one form of transducer in accordance with the principles of this invention;

Figure 2 is a cross-sectional view taken along line 2--2 of Figure 1;

Figure 3 is a longitudinal cross-sectional view of a modified form of transducer;

Figure 4 is a cross-sectional view taken along line 4--4 of Figure 3;

Figure 5 is a cross-sectional view similar to the view shown in Figure 4 of a further embodiment of the invention;

Figure 6 is a longitudinal cross-sectional view of another embodiment of the invention; and

Figure 7 is a cross-sectional view taken along line 7-7 of Figure 6.

Referring to Figures l and 2 of the drawings, the line-above-ground type of waveguide is shown to comprise a first conductor 1, a second conductor 2 spaced apart by a thin strip or layer of dielectric material 3. The two conductors 1 and 2 are preferably of at strip form, the iirst conductor being wider than the second conductor so that propagation of microwave energy therealong is in an approximate TEM mode as hereinbefore explained. The dielectric material may be polystyrene, polyethylene, Teflon, fiberglass or laminated fiberglass impregnated with Teiion, quartz, or other suitable material of high dielectric quality. The conductors 1 and 2 are preferably formed on the dielectric strip by any of the known printed circuit techniques, the one preferred being an electrolytic etching process. l

As shown in Figures 1 and 2, the line-above-ground type of waveguide is extended through a slot 4 contained in one of the walls 5 of a rectangular waveguide 6. While the two waveguides are shown at right angles, it will be clear to those skilled in the art that the lineabove-ground type of waveguide may be disposed at an angle other than with respect to the waveguide'6.

The lirst conductor 1 is connected to the wall 5 and protrudes therebeyond into the rectangular waveguide a suitable distance for impedance matching purposes. In some transducer construction the first conductor 1 may be terminated at the wall 5 but in the present embodiment it is preferred to have the conductor 1 extend part way across the waveguide. The dielectric strip 3 may also terminate part Way across the waveguide but is here shown'as extended all the way across since the strip is normally used as a support for the conductors 1 and 2. The line conductor 2 is extended into the rectangular waveguide in spaced relation to the wall 5, the slot 4 being made suliciently wide to provide proper mechanical and electrical clearance. Adjacent the inner end of the conductor 2 s a conductor 7 disposed crosswise thereof to effect the desired launching ofthe microwave energy fed over the line-above-ground into the rectangular waveguide and vice versa. The conductor 7 may be a separate piece of conductive material attached to the conductor 2 or it may be made integral as shown, it being predetermined and etched at the same time the conductor 2 isfound. The conductor 2 is shown to extend beyond the crosswise conductor 7 to provide a stub 8, which is of such length and width as to provide optimum impedance matching for the operating frequency. The rectangular waveguide is provided with a trap 9 to the backside of the conductor 1 which may be adjusted by plunger 10.

By way of example of the operation of a transducer in accordance with the embodiment of Figures 1 and 2, the following dimensions are hereby furnished of an actual working model designed for 4700 mcs/sec. tangular waveguide was 2" x 1", the conductor 1 was chosen to be 2 wide so as to be received within the The reco liductorlZc, in contact with the conductor 15. '14 and 15 are of such size as to provide proper mechanrespect to walls of the waveguide' 6c.

anfragen 4 timurn impedance matching may be obtained by proper adjustment of the stub 19.of the line conductor 2c extending below the conductor 16 as viewed in the drawings. The trap formed by the end wall 13 is desirable since there may be poor contact between the planar conductor 1c and certain of the walls of the waveguide 6c.

While we have described above theprinciples of our invention in connection `with speciiic apparatus, it is to be `clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention, as set forth in the obiects thereof and in the accompanying claims.

We claim:

1. A transducer for microwave energy comprising a first waveguide of rectangular form in cross-section, a second waveguide comprising a first relatively tlat striplike conductorfa second conductor and a layer of dielecf tric material disposed therebetween to maintain said Frequency, mcs/sec.: V. S. W. R.

i These operating gures represent the results of a laboratory model which no doubt could be further improved by varying the dimensionsY of the conductors 1, 2 Aand`7.

Referring to Figures 3 and 4, the lineaboveground type'of` waveguide is shown to comprise a first conductor la, a second conductor 2a spaced apart by a thin strip or layer of dielectric material 3a, wherein the conductor, v1a extends completely across the rectangular waveguide 6a, and in' fact, forms the end plate for the waveguide. The line 'conductor 2a is shown-provided with a crossbarconductori7a for proper excitation of the launching lield. The conductor 2a is further provided with a conductive post v11 disposed substantially coaxially of the y waveguideand extending in the direction of wave pro- 'In this embodiment it was found that theV conductors in spaced'substantially parallel relation, 'said second conductor being narrower than said first conductor so that the latter presents substantially a planar surface with respect to said second conductor, a wall of said rectangular waveguide having an opening therethrough, said second waveguide being disposed at an angle to said rectangular waveguide with the rs't conductor thereof coupled electrically to the wall having said opening, said layer of dielectric material and said secondconductor being extended through said opening into said rectangular waveguide, said layer ot dielectric material beingextended over substantially the entire cross-section of said rectangular waveguide and means enlarging the lateral area of said second conductor with- The Hcross-bar conductor 7a, however, is believed to y further enhance and insure proper launching of the microwave energy. The'proper impedance matching is obtained by determining the 'dimension of the cross-bar conductor -7a and stub 8.

In Figure -5v a similartransducer to that shown in VFigures 3 and 4 is illustrated wherein the line conductor '2b `isshown with an^enlarged area 12 located substanor any `other desired configurationsuitable for the transfer of energy in the desired mode.

InfFigures 6 and 7 another transducer arrangement fis shown wherein the rectangular waveguide y6c is pro- `vided with a closed -end 13 and apair of aligned slots 14 and 15 `in two opposite walls of the waveguide 6c.

'Aconductor' 16 is disposed crosswise of the waveguide l"slightly offset and at right angles to the plane of the two s1ots`14 and 15, the ends of the conductor 16 Abeing mounted in the side walls 17 and 1S of the waveguide. The line-abovegroundv waveguide comprising conductors 1c and'Zc, spaced by dielectric strip 3c, is received 'through the slots `14'and` 15 with the conductor 1c in contact with the walls of the waveguide and the line con- T he slots ical and electrical spacing ofl the line conductor 2c with n This embodiment `is particularly useful since it provides forh adjustment or the lineaboveground waveguide relative to the-rectangu lar waveguide and the cross conductor 15, whereby opin said rectangular waveguide to enhance the coupling of microwave energy from one to the other of said waveguides.

2. A transducer according to `claim l, wherein the enlarged area of said second conductor includes a post of conductive material disposed axially of said rectangular' waveguide.

3. A transducer according to claim l, wherein the enlarged area of said second conductor includes conductive material disposed laterally with respect to the longitudinal axis of saidrectangular wavegulfe.

4. A transduceraccording to `claim 3, wherein the enlarged area of said second conductor further includes a conductive post disposed axially of said rectangular waveguide. u

5. A tranducer according to claim 3, wherein the enlarged conductor is disposed crosswise of said rectangular waveguide in electrical connection with the side walls thereof.

6. A transducer according to claim 3, wherein the enlarged surface of said second conductor includes an enlarged circular area in the plane of said second conductor.

7. A transducer according to claim 6; wherein the enlarged area of said second conductor further includes a conductive post disposed axially of said rectangular' waveguide. l

8. A transducer according to claim l, wherein said first relatively flat strip-like conductor extends at least part way across said rectangular waveguide.

`9. A Atransducer according to claim l, wherein said firstl relatively at strip-like conductor extends completely across said rectangular waveguide and the enlarged area of said second conductor includes a conductor disposedcrosswise of said rectangular waveguide in electrical connection with said second conductor.

10. A transducer for microwave energy comprising a irst waveguide of rectangular forni in cross-section, a second waveguide comprising a planar conductor of width corresponding tothe width of said `rectangular waveguide, aV at strip vline conductor of narrow width comparedv to the width of said planar conductor and a `layer of dielectric material spacing said conductors in `substantially parallel relation, a wall of said rectangular waveguide having a slot therethrough through which said second waveguide extends with the planar conductor in coupled relation to a Wall of said rectangular waveguide and said line conductor in spaced relation thereto, said layer of dielectric material being extended across said rectangular waveguide and a third conductor disposed at right angles to the line conductor in electrical connection therewith within said rectangular waveguide to enhance the transfer of energy from one waveguide to the other.

l1. A transducer according to claim 10, wherein said line conductor is provided with a post conductor disposed longitudinally Within said rectangular waveguide.

12. A transducer for microwave energy comprising a first waveguide of rectangular form in cross-section, a second waveguide comprising a planar conductor of width corresponding to the width of said rectangular waveguide, a line conductor of narrow width compared to the width of said planar conductor and a layer of dielectric material spacing said conductors in substantially parallel relation, a wall of said rectangular waveguide having a slot therethrough through which said second waveguide extends with the planar conductor incoupled relation to a wall of said rectangular waveguide and said line conductor in spaced relation thereto, a third conductor disposed crosswise of said rectangular waveguide in electrical connection with the side walls thereof and disposed in a plane parallel to the plane of said planar conductor, said second waveguide being adjustable relative to said rst waveguide with the line conductor thereof in electrical contact with said third conductor, the adjustment providing a stub of the line conductor beyond said third conductor for impedance matching purposes.

References Cited in the tile of this patent UNITED STATES PATENTS 2,433,074 Tuller Dec. 23, 1947 2,445,896 Tyrrell July 27, 1948 2,514,678 Southworth July 11, 1950 2,527,146 Mumford Oct. 24, 1950 2,588,103 Fox Mar. 4, 1952 2,611,822 Bliss Sept. 23, 1952 2,658,145 Dorne et al. Nov. 3, 1953 2,735,073 Grieg Feb. 14, 1956 FOREIGN PATENTS 116,110 Australia Nov. 19, 1942 

